Question #4c9b0
1 Answer
Explanation:
In order to find a solution's molality, you must know two things
- the number of moles of solute
- how many kilograms of solvent you have in the solution
You're dealing with a
To make the calculations easier, pick a
Use sodium chloride's molar mass to determine how many moles of solute you have in this sample
#2 color(red)(cancel(color(black)("g"))) * "1 mole NaCl"/(58.44color(red)(cancel(color(black)("g")))) = "0.03422 moles NaCl"#
Now, this solution will also contain
#m_"solution" = m_"solute" + m_"solvent"#
#m_"solvent" = "100 g" - "2 g" = "98 g water"#
This means that its molality will be - do not forget to convert the mass of water from grams to kilograms
#color(blue)(|bar(ul(color(white)(a/a)b = n_"solute"/m_"solvent"color(white)(a/a)|)))#
#b = "0.03422 moles"/(98 * 10^(-3)"kg") = "0.3492 mol kg"^(-1)#
I'll leave the answer rounded to two sig figs, despite the fact that you only have one sig fig for the percent concentration of the solution
#b = color(green)(|bar(ul(color(white)(a/a)"0.35 mol kg"^(-1)color(white)(a/a)|)))#
SIDE NOTE The molality of the solution must be the same regardless of what sample you pick as a starting point.
I highly recommend redoing the calculations for different sample of this solution - the molality will always be equal to